Haiti is under a Hurricane Warning today as Tropical Storm Tomas continues its slow turn in the Caribbean toward the vulnerable island nation. The warning means hurricane conditions - winds of 73 mph or more - are expected somewhere in the warned area late tonight or early Friday. Forecasters have also warned the island to expect a 1- to 3-foot storm surge with "large and destructive waves," and 5 to 10 inches of rain.

At a press briefing this afternoon, National Hurricane Center Diretcor Bill Read said the hurricane-force winds should be limited to Haiti's exposed beaches, and mainly in the form of gusts. The rest of the country will see mostly tropical-storm-force winds, of 39 to 73 mph.

"The predominant threat is the heavy rains," he said, with amounts as high as 15 inches in isolated areas. "Even a five-inch rain can cause significant flash flooding and mudslides throughout the area there."

The wind and rain may find more than a million Haitians in vulnerable tent camps, where they have taken shelter after being displaced from their homes by last January's devastating earthquake. The island has also been grappling with an outbreak of cholera outside of the capital Port au Prince. The disease has killed 492 people and sickened thousands.

The World Health Organization has said the epidemic is not over, and that the country should prepare for it to spread into the crowded capital. 

Phil Gelman, the USAID"s Disaster Assistance Response Team Leader in Haiti, said aid agencies have been prepositioning emergency supplies for Haitians and assembling their own supplies to see them through the storm.

The World Meteorological Organization has also been advising Haitians, in French, to get out of vulnerable, low-lying locations and move into sturdier structures. He said surveys in the camps indicated "a lot of people" said they  do have places to go. But he declined to guess how many will be riding out the storm in the open.

Gelman said efforts have been underway to clear drainage canals and "shore up hillsides" in advance of the storm "in an attempt to reduce the vulnerability of these informal settlements.".

Hurricane Warnings have also been posted today for the province of Guantanamo, in Cuba, the southeastern Bahamas, and the Turks and Caicos Islands.

Tropical Storm Warnings are posted for Jamaica and two other eastern provinces in Cuba. A Tropical Storm Watch is up for the south coast of the Dominican Republic, just east of Haiti on the two countries' shared island of Hispaniola.

The National Hurricane Center said the storm was centered 295 miles west southwest of Port au Prince, moving to the north at 8 mph with top sustained winds of 50 mph. The latest forecast track would take the storm's center between Haiti and Cuba. But that would also place its strongest winds and rains on the east side of the Windward Passage - on Haiti. 

Haitian authorities have urged people to seek safer shelter, and closed schools to reopen them as shelters. But there is little shelter to be had for hundreds of thousands of camp residents. Some have refused to leave without a guarantee of finding a safe shelter. In other parts of the impoverished country, people are living in flimsy homes, along dangerous, flood-prone rivers and on easily eroded hillsides. 

Aid agencies were rushing in emergency supplies, and the U.S. has sent an amphibious ship to the area with 10 helicopters and medical and engineering teams. Read more in the Haitian Times, here.

Here is the latest advisory on Tomas. Here is the forecast storm track. And here is the view from orbit.